Whoever knelt down before the Imam or a (religious) preacher

Narrated Anas bin Malik:

One day Allah's Messenger (ﷺ) came out (before the people) and `Abdullah bin Hudhafa stood up and asked (him) "Who is my father?" The Prophet (ﷺ) replied, "Your father is Hudhafa." The Prophet (ﷺ) told them repeatedly (in anger) to ask him anything they liked. `Umar knelt down before the Prophet (ﷺ) and said thrice, "We accept Allah as (our) Lord and Islam as (our) religion and Muhammad as (our) Prophet." After that the Prophet (ﷺ) became silent.